CONFIG_MACH_CSB726 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

Enable Cogent CSB726 System On a Module

modulename: csb726.ko

configname: CONFIG_MACH_CSB726

Linux Kernel Configuration
└─>PXA2xx/PXA3xx-based
└─>Intel PXA2xx/PXA3xx Implementations
└─>Enable Cogent CSB726 System On a Module
In linux kernel since version 2.6.30 (release Date: 2009-06-09)  
Say Y here if you intend to run this kernel on a Cogent
CSB726 System On Module.

source code:
arch/arm/mach-pxa/csb726.c